WO2021106656A1 - Resin particle dispersion - Google Patents

Abstract

The present invention relates to: a resin particle dispersion containing a core-shell-type resin particle (A) and water, wherein a shell portion resin of the core-shell-type resin particle (A) includes a structural unit derived from a (meth)acrylic acid ester (a-1) having a C4-C8 hydrocarbon group, a core portion resin of the core-shell-type resin particle (A) includes at least 5 mass% of a structural unit derived from a (meth)acrylamide-based monomer (b-1) having a solubility parameter of 17.0-21.0 (J/cm3)0.5, the glass transition temperature of the core resin is at most 50 °C, and the acid value of the core-shell-type resin particle (A) is 50-100 mgKOH/g; a method for producing said resin particle dispersion; and a method for printing by using said resin particle dispersion.

Description

Resin particle dispersion

The present invention relates to a resin particle dispersion, a method for producing the resin particle dispersion, and a printing method using the resin particle dispersion.

Under the circumstances surrounding the printing industry these days, in response to growing awareness of the work environment, printing environment, and work environment, water-soluble inks that use water as the main solvent are required from the viewpoint of low odor and safety. Has been printed. On the other hand, further improvement in printing performance is also required.
Further, there is an increasing demand for white background printing on non-white background materials such as corrugated cardboard, paperboard, and resin film, instead of conventional printing on white background paper base materials. Polyolefin resins, polyester resins, and the like are often used as the resin film base material used for printing, and improvement of coating film physical properties such as substrate adhesion is particularly required for the polyolefin resin base material.
Furthermore, in recent years, in addition to demands for energy saving and reduction of environmental load, reduction of the amount of plastic used has been required due to the problem of marine pollution of plastic waste. Therefore, resin film base materials used for printing are also required. Those with thin thickness are becoming mainstream.

In the case of printing on a base material that is not a white background, white ink is used to express white color and improve visibility. As a pigment used for white ink, titanium oxide having high hiding power is widely used. However, in the case of a water-based ink containing titanium oxide or the like, there is a problem that the adhesion to the base material is lowered.
Here, the water-based ink composition generally contains a pigment, a polymer, and water, and the polymer is added as a dispersant or a binder for the pigment for the purpose of improving the physical characteristics of the coating film of the printed matter. As the binder, resin particles obtained by an emulsification polymerization method or a phase inversion emulsification method are used. In addition, the resin particles may be of a core-shell type in order to exhibit various functions.

For example, Japanese Patent Application Laid-Open No. 2014-205816 (Patent Document 1) describes a core-shell type resin fine particle dispersion that exhibits excellent coating material properties on a resin film base material, and an aqueous solution used for gravure printing or the like containing the same. For the purpose of providing an ink composition, a core-shell type resin fine particle dispersion for water-based ink having a specific average particle size and Tg, which is obtained by polymerizing an ethylenically unsaturated monomer in an aqueous medium in the presence of a water-soluble resin. The body is a water-soluble resin obtained by polymerizing an aromatic ethylenically unsaturated monomer and a carboxyl group-containing ethylenically unsaturated monomer, and is a core-shell type resin particle for water-based ink. Dispersions and aqueous ink compositions are described.
In Japanese Patent Application Laid-Open No. 2019-116535 (Patent Document 2), a specific (meth) acrylic acid ester is derived from a core portion for the purpose of providing a resin particle dispersion that can be used as a water-based ink having excellent substrate adhesion and the like. A core-shell type resin particle dispersion in which a core-shell type resin particle having a specific acid value and a specific amount of the constituent unit of the above is combined with a specific glycol ether is disclosed.

The present invention is a resin particle dispersion containing core-shell type resin particles (A) and water.
The shell resin of the core-shell type resin particles (A) contains a structural unit derived from (meth) acrylic acid ester (a-1) having a hydrocarbon group having 4 or more and 8 or less carbon atoms.
The core resin of the core-shell type resin particles (A) has a (meth) acrylamide-based monomer (b-1) ^{having a solubility parameter of 17.0 (J / cm 3} ) ^0.5 or more and 21.0 (J / cm ³ ) ^{0.5 or less.} ) Derived from 5% by mass or more
The glass transition temperature of the core resin is 50 ° C or less,
The present invention relates to a resin particle dispersion in which the acid value of the core-shell type resin particles (A) is 50 mgKOH / g or more and 100 mgKOH / g or less.

As the water-based ink, an ink that can be printed on various resin film substrates, has high versatility, and has excellent substrate adhesion is desired. Patent Documents 1 and 2 describe that an ink containing core-shell type resin particles has improved the adhesion to a polyolefin resin film substrate.
However, in printing on a printing substrate having low water absorption such as a resin film, it is very thin, has low stiffness (rigidity), and is easily deformed, particularly like a printing substrate having a thickness of 100 μm or less. The more the printed substrate is, the more the substrate adhesion is not sufficient, and improvement thereof is required.
INDUSTRIAL APPLICABILITY The present invention can obtain a printed matter having excellent substrate adhesion even when a printing substrate having a very thin thickness and easily deforming is used for printing on a printing substrate having low water absorption. The present invention relates to a resin particle dispersion, a method for producing the resin particle dispersion, and a printing method using the resin particle dispersion.

The present inventors are a dispersion containing core-shell type resin particles, and the shell portion resin in the outer core of the core-shell type resin particles has a hydrocarbon group having a specific carbon number (meth). The core resin at the core of the core-shell type resin particles contains a structural unit derived from an acrylic acid ester, and further contains a specific amount of a structural unit derived from a (meth) acrylamide-based monomer having a solubility parameter in a specific range. By setting the glass transition temperature of the core resin to a specific value or less and setting the acid value of the core-shell type resin particles to a specific range, the thickness is very thin and easily deformed when printing on a printing substrate having low water absorption. A resin particle dispersion, a method for producing the resin particle dispersion, and a printing method using the resin particle dispersion, which can obtain a printed matter having excellent adhesion to the substrate even when such a printing substrate is used. Found that we can provide.

That is, the present invention relates to the following [1] to [3].
[1] A resin particle dispersion containing core-shell type resin particles (A) and water.
The shell resin of the core-shell type resin particles (A) contains a structural unit derived from (meth) acrylic acid ester (a-1) having a hydrocarbon group having 4 or more and 8 or less carbon atoms.
The core resin of the core-shell type resin particles (A) has a (meth) acrylamide-based monomer (b-1) ^{having a solubility parameter of 17.0 (J / cm 3} ) ^0.5 or more and 21.0 (J / cm ³ ) ^{0.5 or less.} ) Derived from 5% by mass or more
The glass transition temperature of the core resin is 50 ° C or less,
A resin particle dispersion in which the acid value of the core-shell type resin particles (A) is 50 mgKOH / g or more and 100 mgKOH / g or less.
[2] A step of polymerizing a core resin monomer forming a core resin in the presence of an emulsion of a shell polymer forming the shell resin to form core-shell type resin particles (A) to obtain a resin particle dispersion. The method for producing a resin particle dispersion according to the above [1], which comprises I.
[3] A printing method for printing on a resin film as a printing base material using the resin particle dispersion according to the above [1].

According to the present invention, in printing on a printing substrate having low water absorption, it is possible to obtain a printed matter having excellent substrate adhesion even when a printing substrate having a very thin thickness and easily deforming is used. It is possible to provide a resin particle dispersion, a method for producing the resin particle dispersion, and a printing method using the resin particle dispersion.

[Resin particle dispersion]
The resin particle dispersion of the present invention is a resin particle dispersion containing core-shell type resin particles (A) (hereinafter, also referred to as "resin particles (A)") and water, and is a core-shell type resin particles (hereinafter, also referred to as "resin particles (A)"). The shell resin in the outer core of A) contains a structural unit derived from (meth) acrylic acid ester (a-1) having a hydrocarbon group having 4 or more and 8 or less carbon atoms, and is composed of the core-shell type resin particles (A). The core resin in the inner core has a solubility parameter (hereinafter, also referred to as "SP value") of 17.0 (J / cm ³ ) ^0.5 or more and 21.0 (J / cm ³ ) ^0.5 or less (meth) acrylamide type. The constituent unit derived from the monomer (b-1) is contained in an amount of 5% by mass or more, the glass transition temperature of the core resin is 50 ° C. or less, and the acid value of the core-shell type resin particles (A) is 50 mgKOH / g or more and 100 mgKOH / g or less. It is characterized by being.
In the present invention, "(meth) acrylic acid ester" refers to an acrylic acid ester and / or a methacrylic acid ester.
The resin particle dispersion of the present invention can be used as a water-based ink having excellent adhesion to a substrate, and can be further contained with a pigment or the like and used as a water-based ink for printing, particularly for gravure printing. Further, when the resin particle dispersion of the present invention does not contain a pigment, it can be used as a clear ink.

The resin particle dispersion of the present invention has the effect of being able to obtain a printed matter having excellent substrate adhesion. The reason is not clear, but it is inferred as follows.
The core-shell type resin particles having an appropriate acid value can impart stability to the ink by an electrostatic repulsive force. Further, the shell resin in the outer core of the core-shell type resin particles contains a structural unit derived from a (meth) acrylic acid ester having a hydrocarbon group having 4 or more and 8 or less carbon atoms, and the glass transition temperature of the core resin in the inner core. By setting the temperature to 50 ° C. or lower, the adhesion to the base material such as a resin film is improved, and the core-shell structure has an appropriate flexibility, so that the followability to the physical deformation of the base material is improved. It is considered that a certain peel strength can be exhibited.
Generally, in the case of a thick substrate, a strong peel stress is unlikely to occur in the printed coating film, but in the case of a very thin substrate, a strong peel stress is generated in the printed coating film.
In the present invention, a strong cohesive force (intermolecular interaction) is expressed by further introducing an amide structure into the core resin of the core-shell type resin particles, and the resistance to a strong peeling force is improved to increase the thickness. It is considered that the peel strength when a thin base material is used can be improved.
Here, in the present invention, by setting the SP value of the (meth) acrylamide-based monomer used for introducing the amide structure into the core resin in a specific range, the shell resin is used in the formation of the core-shell type resin particles described later. It is efficiently absorbed by a shell polymer having a hydrophobic moiety containing a structural unit derived from a (meth) acrylic acid ester having a hydrocarbon group having 4 or more and 8 or less carbon atoms, and a predetermined amount (meth) is absorbed by the core resin. ) A structural unit derived from an acrylamide-based monomer can be introduced, which is considered to improve the adhesion to the substrate.

<Core-shell type resin particles (A)>
The resin particle dispersion of the present invention contains core-shell type resin particles (A).
The core-shell type resin particles (A) are resin particles having a structure in which the shell portion resin contains the core portion resin.
The core-shell type resin particles (A) may be composed of three or more phases. In this case, among the phases satisfying the above-mentioned constitution, the resin in the innermost core is the core resin, and the resin in the outer core is the shell resin.

(Shell resin)
The shell resin of the core-shell type resin particles (A) is not particularly limited as long as it contains a structural unit derived from (meth) acrylic acid (a-1) having a hydrocarbon group having 4 or more and 8 or less carbon atoms. Condensation resins such as polyester and polyurethane, vinyl polymers and the like can be mentioned.
Among these, a vinyl polymer obtained by addition polymerization of a vinyl monomer (vinyl compound, vinylidene compound, vinylene compound) is preferable, and an acrylic polymer is more preferable, from the viewpoint of improving the adhesion to the substrate. As the vinyl-based polymer, a synthetic polymer may be used as appropriate, or a commercially available product may be used.
The shell resin is preferably a water-insoluble polymer, and more preferably a water-insoluble polymer having a self-emulsifying ability. In particular, when a resin film base material having a polar group on the surface is used as the printing base material by surface treatment such as a corona discharge-treated biaxially stretched polypropylene film, the substrate adhesion is improved. The water-insoluble polymer preferably has an anionic group.

The glass transition temperature of the shell resin is preferably 40 ° C. or higher, more preferably 50 ° C. or higher, still more preferably 60 ° C. or higher, still more preferably 70 ° C. or higher, and from the viewpoint of preventing blocking after printing. It is preferably 180 ° C. or lower, more preferably 150 ° C. or lower, still more preferably 130 ° C. or lower, and even more preferably 110 ° C. or lower. The glass transition temperature can be calculated from the mass fraction of the monomers constituting the shell resin and the glass transition temperature of the homopolymer of each monomer component based on the Fox formula.
The acid value of the shell resin is preferably 100 mgKOH / g or more, more preferably 120 mgKOH / g or more, still more preferably 150 mgKOH / g or more, still more preferably 170 mgKOH / g or more, from the viewpoint of improving the adhesion to the base material. Yes, and preferably 280 mgKOH / g or less, more preferably 260 mgKOH / g or less, still more preferably 250 mgKOH / g or less, still more preferably 200 mgKOH / g or less.
The acid value of the shell resin can be calculated from the mass ratio of the monomers constituting the shell resin.

When the shell resin is a vinyl polymer, particularly an acrylic polymer, the shell resin preferably further contains a structural unit derived from the ionic monomer (a-2). The shell resin contains a structural unit derived from a hydrophobic monomer (a-3) other than the (meth) acrylic acid ester (a-1) and a structural unit derived from a hydrophilic nonionic monomer (a-4). You may.
The shell resin is, for example, a (meth) acrylic acid ester (a-1), and if necessary, an ionic monomer (a-2), a hydrophobic monomer (a-3), and a hydrophilic nonionic monomer (a). It can be obtained by addition polymerization of a shell resin monomer containing one or more selected from -4) by a known method.

[(Meta) acrylic acid ester (a-1)]
The (meth) acrylic acid ester (a-1) has a hydrocarbon group having 4 to 8 carbon atoms and is used as a monomer component of the shell resin from the viewpoint of improving the dispersion stability of the resin particles (A). Be done. Examples of the (meth) acrylic acid ester (a-1) include alkyl (meth) acrylates, aromatic group-containing (meth) acrylates, and the like, and more preferably alkyl (meth) acrylates.
The alkyl (meth) acrylate preferably has an alkyl group having 4 or more and 8 or less carbon atoms, more preferably 4 or more and 6 or less carbon atoms, and for example, (iso or tertiary) butyl (meth) acrylate, (iso). ) Amil (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate and the like can be mentioned.
In addition, "(iso or tertiary)" and "(iso)" mean both the case where these groups are present and the case where these groups are not present, and when these groups are not present, they indicate normal. Further, "(meth) acrylate" indicates acrylate and / or methacrylate.
As the aromatic group-containing (meth) acrylate, one or more selected from benzyl (meth) acrylate, phenoxyethyl (meth) acrylate and the like are preferable, and benzyl (meth) acrylate is more preferable.

[Ionic monomer (a-2)]
The ionic monomer (a-2) is used as a monomer component of the shell resin from the viewpoint of improving the dispersion stability of the resin particles (A).
Examples of the ionic monomer (a-2) include an anionic monomer and a cationic monomer, and an anionic monomer is preferable.
Examples of the anionic monomer include a carboxylic acid monomer, a sulfonic acid monomer, and a phosphoric acid monomer.
Among the anionic monomers, a carboxylic acid monomer having a carboxy group is preferable from the viewpoint of improving the dispersion stability of the resin particles (A), and acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid are preferable. , Citraconic acid, 2-methacryloyloxymethylsuccinic acid and the like are more preferable, and one or more selected from acrylic acid and methacrylic acid are further preferable.
Examples of the cationic monomer include N, N-dimethylaminoethyl methacrylate and N, N-dimethylaminoethyl acrylamide.
The ionic monomer (a-2) includes a monomer such as an acid or an amine that is not an ion in a neutral state but becomes an ion under acidic or alkaline conditions.

[Hydrophobic monomer (a-3)]
The hydrophobic monomer (a-3) other than the (meth) acrylic acid ester (a-1) may be used as a monomer component of the shell resin from the viewpoint of improving the dispersion stability of the resin particles (A). Examples of the hydrophobic monomer (a-3) include alkyl (meth) acrylates and styrene-based monomers other than the (meth) acrylic acid ester (a-1).
For example, examples of the alkyl (meth) acrylate other than the (meth) acrylic acid ester (a-1) include methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, and (iso) decyl (meth). ) Acrylate, (iso) dodecyl (meth) acrylate, (iso) stearyl (meth) acrylate and the like.
As the styrene-based monomer, one or more selected from styrene, 2-methylstyrene, divinylbenzene and the like are preferable, and styrene is more preferable.

[Hydrophilic nonionic monomer (a-4)]
The hydrophilic nonionic monomer (a-4) can be used as a monomer component of the shell resin from the viewpoint of improving the dispersion stability of the resin particles (A).
Examples of the hydrophilic nonionic monomer (a-4) include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate and 3-hydroxypropyl (meth) acrylate; polypropylene glycol (n = 2 to 30, n). The average number of moles of oxyalkylene groups added is shown below. The same applies hereinafter. Polyalkylene glycol (meth) acrylates such as (meth) acrylate and polyethylene glycol (meth) acrylate (n = 2 to 30); methoxypolyethylene glycol (n = 1 to 1 to 30). 30) Alkoxypolyalkylene glycol (meth) acrylates such as (meth) acrylates and octoxypolyethylene glycols (n = 1-30) (meth) acrylates; phenoxy (ethylene glycol / propylene glycol copolymerization) (n = 1-30, Among them, ethylene glycol: n = 1-29) (meth) acrylate and the like can be mentioned.
Specific examples of commercially available hydrophilic nonionic monomers (a-4) include NK Ester M-20G, 40G, 90G, 230G, etc. of Shin Nakamura Chemical Industry Co., Ltd. Blemmer PE-90, 200, 350, PME-100, 200, 400, etc., PP-500, 800, 1000, etc., AP-150, 400, 550, etc., 50PEP-300, 50 POEP- 800B, 43PAPE-600B and the like can be mentioned.
The monomer components of the shell resin mentioned above can be used alone or in combination of two or more.
The shell resin may contain a structural unit derived from a monomer other than the monomer components listed above as long as the effect of the present invention is not impaired.

(Content of each component in shell resin monomer or content of each structural unit in shell resin)
The content of the shell resin monomer during the production of the shell resin (content as an unneutralized amount; the same applies hereinafter) or the content of the structural unit derived from each component in the shell resin is in close contact with the base material. From the viewpoint of improving the sex, it is as follows.
The content of the (meth) acrylic acid ester (a-1) is preferably 40% by mass or more, more preferably 50% by mass or more, further preferably 60% by mass or more, and preferably 95% by mass or less. It is more preferably 90% by mass or less, still more preferably 85% by mass or less.
The content of the ionic monomer (a-2) is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and preferably 60% by mass or less, more preferably. It is 50% by mass or less, more preferably 40% by mass or less.
The total content of the (meth) acrylic acid ester (a-1) and the ionic monomer (a-2) is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more. It is more preferably 95% by mass or more, preferably 100% by mass or less, and even more preferably 100% by mass.

(Core resin)
The core resin has a (meth) acrylamide-based monomer (b) ^{having an SP value of 17.0 (J / cm 3} ) ^0.5 or more and 21.0 (J / cm ³ ) ^0.5 or less from the viewpoint of improving the adhesion to the base material. -1) Includes the building blocks of origin.

[(Meta) Acrylamide Monomer (b-1)]
In the present invention, the SP value of the (meth) acrylamide-based monomer (b-1) is the Hansen solubility parameter (HSP value), and the calculation software “Hansen Solubility Parameter in Practice (HSPiP) Version 5.2.02” is used. Use the calculated value.
^{The SP value is 17.0 (J / cm 3} ) ^0.5 or more, preferably 17.3 (J / cm ³ ) ^0.5 or more, and more preferably 17.5 (17.5) from the viewpoint of improving the adhesion to the substrate. J / cm ³ ) ^0.5 or more and 21.0 (J / cm ³ ) ^0.5 or less, preferably 20.7 (J / cm ³ ) ^0.5 or less, more preferably 20.5 (J / cm) ³ ) ^{It is 0.5} or less.

Examples of the (meth) acrylamide-based monomer (b-1) include N-tert-butylacrylamide (SP value: 20.2), N-tert-octylacrylamide (SP value: 17.9), and N- (2-ethylhexyl). ) Acrylamide (SP value: 19.4), Nn-octylacrylamide (SP value: 19.8), N-dodecylacrylamide (SP value: 18.5), Nn-heptylacrylamide (SP value: 20) .3), N-alkyl (meth) acrylamide with linear, branched or cyclic alkyl groups such as N-hexyl acrylamide (SP value: 20.6), N-cyclohexylmethacrylamide (SP value: 20.6). Aromatic group-containing (meth) acrylamide such as N, N-dibenzylacrylamide (SP value: 20.4); N-alkoxymethyl (meth) such as N-isobutoxymethylacrylamide (SP value: 20.8) Examples include acrylamide.
The unit of the SP value is "(J / cm ³ ) ^0.5 ". In addition, (meth) acrylamide represents acrylamide and / or methacrylamide.
The (meth) acrylamide-based monomer (b-1) may be used alone or in combination of two or more.

Among these, from the viewpoint of improving the adhesion to the substrate, N-alkyl (meth) acrylamide having a linear, branched or cyclic alkyl group is preferable, and N-alkylacrylamide having a branched alkyl group is more preferable. Yes, more preferably an N-alkyl acrylamide having a branched alkyl group having 4 or more and 8 or less carbon atoms, and even more preferably one or more selected from N-tert-butyl acrylamide and N-tert-octyl acrylamide. ..

[(Meta) acrylic acid ester (b-2)]
The core resin preferably further contains a structural unit derived from a (meth) acrylic acid ester (b-2) having a hydrocarbon group having 2 or more and 18 or less carbon atoms. The hydrocarbon group having 2 or more and 18 or less carbon atoms in the (meth) acrylic acid ester (b-2) may contain a hetero atom such as an oxygen atom or a nitrogen atom. The carbon number of the hydrocarbon group of the (meth) acrylic acid ester (b-2) is preferably 3 or more, more preferably 4 or more, and preferably 12 or less, from the viewpoint of substrate adhesion. It is preferably 8 or less.

As the hydrocarbon group of the (meth) acrylic acid ester (b-2), an alkyl group and an aryl group are preferable, and for example, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group and a tert -Butyl group, pentyl group, hexyl group, heptyl group, octyl group, 2-ethylhexyl group, octadecyl group, cyclohexyl group, benzyl group and the like can be mentioned.
The hydrocarbon group of the (meth) acrylic acid ester (b-2) is preferably one or more selected from an alkyl group having 3 or more and 12 or less carbon atoms and a benzyl group from the viewpoint of substrate adhesion. , More preferably one or more selected from a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a hexyl group, an octyl group, a 2-ethylhexyl group, an octadecyl group, a cyclohexyl group, and a benzyl group, more preferably. , Butyl group, isobutyl group, sec-butyl group, tert-butyl group, hexyl group, octyl group, 2-ethylhexyl group, and benzyl group, and more preferably isobutyl group.
The (meth) acrylic acid ester (b-2) is one or more selected from acrylic acid ester and methacrylic acid ester, and acrylic acid ester is preferable from the viewpoint of substrate adhesion. The (meth) acrylic acid ester (b-2) may be used alone or in combination of two or more.

The (meth) acrylic acid ester (b-2) having a hydrocarbon group having 2 to 18 carbon atoms is preferably a butyl (meth) acrylate, an isobutyl (meth) acrylate, a secondary butyl (meth) acrylate, or a tertiary butyl (). One or more selected from meta) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and benzyl (meth) acrylate, more preferably isobutyl (meth) acrylate and secondary butyl. It is one or more selected from (meth) acrylate, tertiary butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and benzyl (meth) acrylate, and more preferably isobutyl (meth) acrylate.

(Content of each component in the core resin monomer or content of each structural unit in the core resin)
The content in the core resin monomer during the production of the core resin (content as an unneutralized amount; the same applies hereinafter), or the content of the constituent units derived from each component in all the constituent units constituting the core resin. The amount is as follows from the viewpoint of improving the adhesion to the base material.
The content of the (meth) acrylamide-based monomer (b-1) is 5% by mass or more, preferably 7% by mass or more, more preferably 10% by mass or more, and from the viewpoint of improving the adhesion to the substrate, and It is preferably 60% by mass or less, more preferably 50% by mass or less, still more preferably 40% by mass or less, still more preferably 30% by mass or less, still more preferably 20% by mass or less.
When the core resin contains a structural unit derived from a (meth) acrylic acid ester (b-2) having a hydrocarbon group having 2 or more and 18 or less carbon atoms, the content of the (meth) acrylic acid ester (b-2). Is preferably 30% by mass or more, more preferably 40% by mass or more, still more preferably 50% by mass or more, still more preferably 70% by mass or more, and preferably 95% by mass or less, more preferably. It is 93% by mass or less, more preferably 90% by mass or less.
The total content of the (meth) acrylamide-based monomer (b-1) and the (meth) acrylic acid ester (b-2) is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass. As mentioned above, it is more preferably 95% by mass or more, and preferably 100% by mass or less, still more preferably 100% by mass.
Mass ratio of the content of the (meth) acrylamide-based monomer (b-1) to the (meth) acrylate-based monomer (b-2) [(meth) acrylamide-based monomer (b-1) / (meth) acrylic acid ester (b-1) -2)] is preferably 0.01 or more, more preferably 0.03 or more, still more preferably 0.05 or more, still more preferably 0.07 or more, and preferably 0.5 or less, more. It is preferably 0.3 or less, more preferably 0.2 or less, still more preferably 0.15 or less, still more preferably 0.13 or less.

Since the core resin is the stress concentration point of the resin particles (A), the glass transition temperature thereof is 50 ° C. or lower, preferably 40 ° C. or lower, more preferably 35 ° C. or lower, from the viewpoint of stress relaxation. More preferably 30 ° C. or lower, even more preferably 25 ° C. or lower, even more preferably 10 ° C. or lower, and preferably -13 ° C. or higher, more preferably -10 ° C. or higher, still more preferably -7 ° C. or higher. is there. The glass transition temperature can be calculated from the mass fraction of the monomers constituting the core resin and the glass transition temperature of the homopolymer of each monomer component based on the Fox formula.
The acid value of the core resin is preferably 50 mgKOH / g or less, more preferably 30 mgKOH / g or less, still more preferably 10 mgKOH / g or less, still more preferably 0 mgKOH / g, from the viewpoint of improving the adhesion to the base material. ..
The acid value of the core resin can be calculated from the mass ratio of the monomers constituting the core resin.

[Manufacturing method of resin particle dispersion]
In the method for producing a resin particle dispersion of the present invention, the core resin monomer forming the core resin is polymerized in the presence of an emulsion of the shell polymer forming the shell resin to form the core shell type resin particles (A). The production method including the step I for obtaining the resin particle dispersion is preferable. In the production method, a shell containing a core resin monomer containing a (meth) acrylamide-based monomer (b-1) having an SP value in a specific range and a structural unit derived from the (meth) acrylic acid ester (a-1). By polymerizing in the presence of the polymer emulsion, the hydrophobic shell polymer is used as seed particles, and the core resin monomer is rapidly absorbed inside the seed particles in the emulsion, and the polymerization of the core resin monomer proceeds. , Core-shell type resin particles (A) can be formed.
The shell polymer preferably contains the same structural unit as the shell resin. That is, the shell polymer contains a structural unit derived from a (meth) acrylic acid ester (a-1) having a hydrocarbon group having 4 or more and 8 or less carbon atoms, and the composition and content of the structural unit derived from the monomer contained in the shell polymer. The amount is the same as that of the shell resin described above.

As a method for producing the resin particle dispersion, in step I, specifically, an emulsion of the shell polymer forming the shell resin and an aqueous medium are mixed, and then a core resin monomer forming the core resin is added. Then, the temperature is raised while stirring, and a water-soluble polymerization initiator is further added dropwise to cause a reaction to form core-shell type resin particles (A), which is preferably carried out by a method of obtaining a resin particle dispersion.
After the reaction is started, the formation of particle nuclei is confirmed by changing the hue in the reaction vessel, and then the core resin monomer is further dropped to continue the reaction to obtain the desired core-shell type resin particles (A). be able to.
The core resin monomer may be dropped directly into the reaction vessel, or may be dropped after being made into an emulsion in advance with an aqueous medium. The shell polymer acts as a protective colloid in an aqueous medium and stabilizes the resulting particle core (core). The resin particle dispersion of the present invention obtained by this method has a viscosity close to that of Newtonian and is therefore excellent in printability.
Further, by appropriately changing the composition of the core resin monomer stepwise, it is possible to manufacture a core composed of a plurality of phases or a core whose composition continuously changes from the innermost core.

The aqueous medium used for producing the resin particle dispersion means a medium in which water occupies the largest proportion.
As the water-soluble polymerization initiator, known ones can be used. For example, inorganic peroxides such as potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, azo initiators such as 2,2'-azobis (2-amidinopropane) dihydrochloride, and even peroxide compounds. Examples thereof include a redox initiator in which a reducing agent such as sodium sulfite is combined with the redox initiator.
At the time of polymerization, surfactants such as nonionic surfactants, anionic surfactants, and cationic surfactants can be used, but the formation of particles consisting only of the core resin monomer is suppressed. From the viewpoint of efficiently forming core-shell type resin particles, it is preferable not to use a surfactant.
Preferred polymerization conditions vary depending on the type of polymerization initiator and the like, but the polymerization temperature is preferably 50 ° C. or higher and 90 ° C. or lower, and the polymerization time is preferably 1 hour or longer and 20 hours or lower. The polymerization atmosphere is preferably a nitrogen gas atmosphere or an inert gas atmosphere such as argon.
Since the obtained resin particle dispersion contains at least core-shell type resin particles (A) and water, the solvent used for producing the resin particle dispersion is not removed as it is from the viewpoint of compoundability in the water-based ink. It is preferable to use it.

[Manufacturing of shell polymer emulsion]
As the shell polymer to be the shell resin of the resin particles (A), a shell polymer obtained by appropriately synthesizing a shell resin monomer by a known polymerization method may be used, or a commercially available product may be used.
As a method for producing a shell polymer emulsion, a method of adding a shell polymer to an aqueous medium and performing a dispersion treatment by a disperser or the like, a method of gradually adding an aqueous medium to an organic solvent solution containing the shell polymer, and a method of phase inversion emulsification, etc. Can be mentioned. Among these, the method by transfer emulsification is preferable from the viewpoint of ease of operation.

In the method by transfer emulsification, the solution polymerization method is preferable as the polymerization method of the shell polymer. Thereby, the obtained shell polymer solution can be used for transfer emulsification.
The organic solvent used in the solution polymerization method is not limited, but polar organic solvents such as aliphatic alcohols having 1 to 3 carbon atoms, ketones having 3 to 8 carbon atoms, ethers, and esters are preferable, and specifically. Examples include methanol, ethanol, acetone, and methyl ethyl ketone, with methyl ethyl ketone being more preferred.
At the time of polymerization, a polymerization initiator or a polymerization chain transfer agent can be used, but as the polymerization initiator, an azo compound is preferable, and 4,4'-azobis (4-cyanovaleric acid), 2,2' -Azobis (2,4-dimethylvaleronitrile) and the like are more preferable. As the polymerization chain transfer agent, mercaptans are preferable, and 3-mercaptopropionic acid, 2-mercaptoethanol and the like are more preferable.

Preferred polymerization conditions vary depending on the type of polymerization initiator and the like, but the polymerization temperature is preferably 50 ° C. or higher and 90 ° C. or lower, and the polymerization time is preferably 1 hour or longer and 20 hours or lower. The polymerization atmosphere is preferably a nitrogen gas atmosphere or an inert gas atmosphere such as argon.
After completion of the polymerization reaction, the produced shell polymer can be isolated from the reaction solution by a known method such as reprecipitation and solvent distillation. In addition, unreacted monomers and the like can be removed from the obtained shell polymer by reprecipitation, membrane separation, chromatographic method, extraction method and the like.
From the viewpoint of improving the productivity of the resin particle dispersion, the shell resin is preferably used as it is as a shell polymer solution without removing the solvent used in the polymerization reaction.
The solid content concentration of the shell polymer solution is preferably 20% by mass or more, more preferably 25% by mass or more, still more preferably 30% by mass or more, and preferably 30% by mass or more, from the viewpoint of improving the productivity of the resin particle dispersion. Is 70% by mass or less, more preferably 65% by mass or less, still more preferably 60% by mass or less. The solid content concentration of the shell polymer solution is measured by the method described in Examples.

In the present invention, when the shell polymer is an anionic polymer, it is preferable to use a neutralizing agent to neutralize the anionic groups in the shell polymer. When a neutralizing agent is used, it is preferable to neutralize the pH so that the pH is 7 or more and 11 or less.
Examples of the neutralizing agent include alkali metal hydroxides, ammonia, organic amines and the like. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide. Examples of the organic amine include trimethylamine, ethylamine, diethylamine, triethylamine, triethanolamine and the like.
From the viewpoint of improving the adhesion to the base material, the neutralizing agent is preferably alkali metal hydroxide such as sodium hydroxide or ammonia, and more preferably sodium hydroxide.

The neutralizing agent is preferably used as an aqueous neutralizing agent from the viewpoint of sufficiently and uniformly promoting neutralization. From the same viewpoint as above, the concentration of the neutralizing agent aqueous solution is preferably 3% by mass or more and 30% by mass or less.
The degree of neutralization of the anionic group of the shell polymer is preferably 30 mol% or more, more preferably 40 mol% or more, still more preferably 50 mol% or more, and preferably 50 mol% or more, from the viewpoint of improving the adhesion to the substrate. Is 300 mol% or less, more preferably 200 mol% or less, still more preferably 150 mol% or less.
Here, the degree of neutralization is obtained by dividing the molar equivalent number of the neutralizing agent by the molar equivalent number of the anionic group of the shell polymer.

The weight average molecular weight of the shell polymer is preferably 6,000 or more, more preferably 8,000 or more, still more preferably 10,000 or more, and from the viewpoint of improving the dispersion stability of the resin particles (A). It is preferably 300,000 or less, more preferably 200,000 or less, still more preferably 100,000 or less, still more preferably 50,000 or less. The weight average molecular weight can be measured by the method described in Examples.

The mass ratio of the content of the core resin to the shell resin in the core-shell type resin particles (A) [core resin / shell resin] is preferably 0.6 or more from the viewpoint of improving the adhesion to the base material. More preferably 0.8 or more, still more preferably 1 or more, and preferably 3.0 or less, more preferably 2.7 or less, still more preferably 2.5 or less, still more preferably 2.3 or less. is there.

The acid value of the core-shell type resin particles (A) is the acid value of the resin as a whole constituting the core portion and the shell portion, and is 50 mgKOH / g or more, preferably 55 mgKOH / g, from the viewpoint of improving the adhesion to the base material. It is g or more, more preferably 60 mgKOH / g or more, and 100 mgKOH / g or less, preferably 95 mgKOH / g or less, more preferably 90 mgKOH / g or less.
The acid value of the core-shell type resin particles (A) can be calculated from the mass ratio of the constituent monomers. Further, the core-shell type resin particles (A) can be dissolved or swollen in a suitable organic solvent (for example, methyl ethyl ketone) and measured according to the neutralization titration method of JIS K0070.

The average particle size of the core-shell type resin particles (A) in the resin particle dispersion is preferably 10 nm or more, more preferably 20 nm or more, still more preferably 40 nm or more, and from the viewpoint of improving the adhesion to the substrate. It is preferably 150 nm or less, more preferably 120 nm or less, and even more preferably 100 nm or less.
The average particle size in the resin particle dispersion is measured by the method described in Examples.

The solid content concentration of the resin particle dispersion of the present invention is preferably 15% by mass or more, more preferably 20% by mass or more, still more preferably 25% by mass or more, and from the viewpoint of compoundability in the water-based ink. It is preferably 60% by mass or less, more preferably 50% by mass or less, and further preferably 40% by mass or less.
The solid content concentration of the resin particle dispersion is measured by the method described in Examples.

<Pigment>
The resin particle dispersion of the present invention can contain a pigment. Pigments include white pigments such as titanium oxide, black pigments such as carbon black, azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, and anthraquinone. Examples include chromatic pigments such as pigments and quinophthalone pigments.
From the viewpoint of substrate adhesion, the resin particle dispersion of the present invention preferably contains a white pigment that is often used as a pigment for a background color, and is particularly useful when titanium oxide is used as a pigment.

(Titanium oxide)
The crystal structure of titanium oxide includes rutile type (tetragonal crystal), anatase type (tetragonal crystal), and brookite type (orthorhombic crystal). From the viewpoint of crystal stability, concealment, and availability, the present invention Then, it is preferable to use rutile-type titanium oxide (hereinafter, also simply referred to as "titanium oxide").
Titanium oxide can be produced by the vapor phase method or the liquid phase method, but titanium oxide produced by the vapor phase method is more preferable because it is easy to obtain one having high crystallinity.
Although untreated titanium oxide can be used, surface-treated titanium oxide is preferable from the viewpoint of sealing the photocatalytic activity and obtaining good dispersibility. Examples of the surface treatment of titanium oxide include surface treatment with an inorganic substance and surface treatment with an organic substance such as a titanium coupling agent and a silane coupling agent, but surface treatment with an inorganic substance is preferable.
As a surface treatment method using an inorganic substance of titanium oxide, a method of treating with one or more selected from _{alumina (Al 2} O ₃ ), silica (SiO ₂ ), zinc oxide (ZnO), zirconia (ZrO _{2) and the like is more suitable.} preferable.
By firing the surface-treated titanium oxide powder at 800 to 1000 ° C., sintering between particles can be suppressed, and the fluidity and dispersibility of the secondary particle size can be improved.

The particle shape of titanium oxide is granular, needle-like, or the like and is not particularly limited, but the average primary particle size is an arithmetic average of the major axis of the primary particles from the viewpoint of whiteness, preferably 40 nm or more, more preferably 100 nm. Above, it is more preferably 150 nm or more, still more preferably 200 nm or more, and from the viewpoint of concealment, it is preferably 600 nm or less, more preferably 500 nm or less, still more preferably 400 nm or less.
The average primary particle size of titanium oxide is an arithmetic mean of the major axis of the primary particles, and is measured by the method described in Examples.
Examples of commercially available rutile-type titanium dioxide products are: Ishihara Sangyo Co., Ltd. product name: Typake R, CR, PF series, Sakai Chemical Industry Co., Ltd. product name: R series, TAYCA Corporation product name: JR , MT series, trade name: KURONOS KR series manufactured by Titan Kogyo Co., Ltd., trade name: TR series manufactured by huntsmann, etc.

[Titanium oxide dispersion]
Titanium oxide is preferably blended in the resin particle dispersion of the present invention as a titanium oxide dispersion. That is, when the resin particle dispersion of the present invention further contains titanium oxide as a pigment, the titanium oxide dispersion is further added and mixed with the resin particle dispersion obtained in the above step I to obtain titanium oxide. It is preferable to obtain it as a resin particle dispersion containing.
Titanium oxide is preferably dispersed with a polymer dispersant, and the polymer dispersant for dispersing titanium oxide is not particularly limited, but can be used as a monomer component of the shell portion resin of the core-shell type resin particles (A). A possible polymer containing a structural unit derived from an ionic monomer (a-2) is preferable, and a structural unit derived from a (meth) acrylic acid ester (a-1) or a hydrophobic monomer (a-3), and a hydrophilic nonion. A polymer containing at least one selected from the structural units derived from the sex monomer (a-4) is more preferable, and the structural unit derived from the ionic monomer (a-2) and the constitution derived from the hydrophilic nonionic monomer (a-4). Polymers containing units are more preferred.

As a preferable example of the polymer dispersant for dispersing titanium oxide, from the viewpoint of dispersion stability, the ionic monomer (a-2) is preferably an anionic monomer, more preferably a carboxylic acid monomer, and further preferably acrylic. One or more selected from acid and methacrylic acid, and the hydrophilic nonionic monomer (a-4) is preferably one or more selected from polyalkylene glycol (meth) acrylate and alkoxypolyalkylene glycol (meth) acrylate. Yes, more preferably a polymer of methoxypolyethylene glycol (n = 1-30) (meth) acrylate is more preferred.
In this case, from the viewpoint of dispersion stability, the content of the structural unit derived from the ionic monomer (a-2) component in the polymer dispersant is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably. Is 15% by mass or more, and preferably 35% by mass or less, more preferably 30% by mass or less, still more preferably 25% by mass or less.
From the same viewpoint as above, the content of the structural unit derived from the hydrophilic nonionic monomer (a-4) in the polymer dispersant is preferably 65% by mass or more, more preferably 70% by mass or more, still more preferably 75. It is 5% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, and further preferably 85% by mass or less.
The method for producing the polymer dispersant is preferably the same as the method for producing the shell polymer.

The titanium oxide dispersion can be obtained by dispersing a mixture containing titanium oxide, a polymer dispersant, and an aqueous medium containing water as a main component.
The dispersion treatment can be carried out by a known method using a kneader such as a roll mill or a kneader, a high-pressure homogenizer such as a microfluidics (manufactured by Microfluidics), a paint shaker, a media type disperser such as a bead mill, or the like.
When the polymer dispersant has a carboxy group which is a salt-forming group, it is preferable to neutralize at least a part of the carboxy group with a neutralizing agent such as an alkali metal hydroxide.

The content of the polymer dispersant in the titanium oxide dispersion is preferably 0.5 parts by mass or more, more preferably 0.5 parts by mass or more, based on 100 parts by mass of titanium oxide, from the viewpoint of dispersion stability and print density of the titanium oxide dispersion. Is 1.0 part by mass or more, more preferably 1.3 part by mass or more, still more preferably 1.8 part by mass or more, and preferably 7 part by mass or less, more preferably 6.5 part by mass or less. It is more preferably 6.0 parts by mass or less, still more preferably 5.5 parts by mass or less, still more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less.
The content of water in the titanium oxide dispersion is preferably 30% by mass or more, more preferably 40% by mass or more, and preferably 70% by mass or less, more preferably 60% by mass, from the viewpoint of reducing the environmental load. % Or less.
The average particle size of the titanium oxide particles in the titanium oxide dispersion is preferably 150 nm or more, more preferably 180 nm or more, still more preferably 200 nm or more, and preferably 700 nm or less, more preferably 700 nm or less, from the viewpoint of print density. It is 600 nm or less, more preferably 500 nm or less. The average particle size of the titanium oxide dispersion is measured by the method described in Examples.
The solid content concentration (nonvolatile component concentration) of the titanium oxide dispersion is preferably 30% by mass or more, more preferably 40% by mass or more, and preferably 70% by mass or less, more preferably 70% by mass or less, from the viewpoint of dispersion stability. Is 60% by mass or less.
The solid content concentration of the dispersion of the pigment such as titanium oxide is measured by the method described in Examples.

<Water-soluble organic solvent>
The resin particle dispersion of the present invention can contain a water-soluble organic solvent. Examples of the water-soluble organic solvent include dihydric or higher polyhydric alcohols such as glycol ether, alcohol and glycol, pyrrolidone, alkanolamine and the like, but glycol ether and glycol are preferable from the viewpoint of substrate adhesion. These water-soluble organic solvents may be used alone or in combination of two or more.

The resin particle dispersion of the present invention preferably contains glycol ether from the viewpoint of plasticizing the core-shell type resin particles (A) and improving the adhesion to the base material.
The glycol ether preferably has at least one hydrocarbon group having 2 or more and 8 or less carbon atoms.
As the glycol ether, an alkylene glycol monoalkyl ether such as a monoalkylene glycol monoalkyl ether, a dialkylene glycol monoalkyl ether, or a trialkylene glycol monoalkyl ether, which has 2 or more and 8 or less carbon atoms in the hydrocarbon group of the ether portion; Examples thereof include alkylene glycol dialkyl ethers such as monoalkylene glycol dialkyl ethers and dialkylene glycol dialkyl ethers.
Examples of the polyalkylene glycol portion of glycol ether include an ethylene oxide adduct, a propylene oxide adduct, and a mixed adduct of ethylene oxide and propylene oxide, and an ethylene oxide adduct is preferable.
Among these, alkylene glycol monoalkyl ether is preferable from the viewpoint of improving drying property and leveling property, and ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, ethylene glycol hexyl ether, diethylene glycol monoethyl ether, More preferably, one or more selected from diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monohexyl ether, triethylene glycol monobutyl ether, and ethylene glycol monobenzyl ether.

Examples of the glycol include ethylene glycol, 1,2-propanediol, 1,2-butanediol, 1,2-hexanediol, 1,3-propanediol, 1,3-butanediol, diethylene glycol and the like. , 2-Propanediol, diethylene glycol and other alcandiols having 3 or more and 4 or less carbon atoms are preferable.

<Contents of each component in the resin particle dispersion>
The content of each component in the resin particle dispersion of the present invention is as follows from the viewpoint of improving the adhesion to the base material.
The content of the core-shell type resin particles (A) in the resin particle dispersion is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and preferably 50% by mass or more. Hereinafter, it is more preferably 40% by mass or less, still more preferably 35% by mass or less.
The content of water in the resin particle dispersion is preferably 30% by mass or more, more preferably 40% by mass or more, still more preferably 45% by mass or more, still more preferably 50% by mass or more, from the viewpoint of reducing the environmental load. , More preferably 53% by mass or more, and preferably 80% by mass or less, more preferably 75% by mass or less, still more preferably 70% by mass or less, still more preferably 65% by mass or less.

When the resin particle dispersion further contains a pigment, the content of the pigment in the resin particle dispersion is preferably 3% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass from the viewpoint of print density. % Or more, and preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, still more preferably 20% by mass or less.
When the resin particle dispersion further contains a water-soluble organic solvent, the content of the water-soluble organic solvent in the resin particle dispersion is preferably 0.2% by mass or more, more preferably 0.5% by mass or more, and further. It is preferably 0.8% by mass or more, and preferably 30% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less.

When the resin particle dispersion further contains a pigment, the mass ratio of the pigment content to the core-shell type resin particles (A) in the resin particle dispersion [pigment / core-shell type resin particles (A)] is the print density. From the viewpoint, preferably 0.3 or more, more preferably 0.5 or more, still more preferably 0.8 or more, still more preferably 1.0 or more, still more preferably 1.3 or more, still more preferably 1. It is 5 or more, more preferably 1.8 or more, and from the viewpoint of substrate adhesion, it is preferably 4 or less, more preferably 3 or less, still more preferably 2.5 or less.
When the resin particle dispersion further contains a water-soluble organic solvent, the mass ratio of the content of water to the water-soluble organic solvent in the resin particle dispersion [water / water-soluble organic solvent] is preferably 0.5 or more. , More preferably 1 or more, still more preferably 2 or more, even more preferably 2.5 or more, and preferably 100 or less, more preferably 50 or less, still more preferably 30 or less, still more preferably 10 or less. It is even more preferably 5 or less, and even more preferably 3.5 or less.
In the present invention, the resin particle dispersion containing the pigment can be used as it is as an ink.

[Aqueous ink]
The resin particle dispersion of the present invention can be used as a water-based ink such as an ink for inkjet recording, an ink for gravure printing, and an ink for flexo printing, but is used as a water-based ink for gravure printing from the viewpoint of substrate adhesion. Is preferable.
The water-based ink may further include surfactants, moisturizers, wetting agents, wetting / penetrating agents, dispersants, viscosity modifiers, defoaming agents, preservatives, fungicides, rust preventives and the like, if necessary. Various additives can be mixed and prepared.
The contents of the core-shell type resin particles (A), water, pigment, and water-soluble organic solvent in the water-based ink are basically the same as the contents in the resin particle dispersion.

Examples of the surfactant used in the water-based ink include anionic surfactant, nonionic surfactant, amphoteric surfactant and the like. Among these, a nonionic surfactant is preferable, one or more selected from an acetylene glycol-based surfactant and a polyether-modified silicone-based surfactant is more preferable, and an acetylene glycol-based surfactant is further preferable.
As acetylene glycol-based surfactants, 2,4,7,9-tetramethyl-5-decine-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, and 2,5 Examples thereof include one or more acetylene glycols selected from -dimethyl-3-hexin-2,5-diols, and ethylene oxide adducts of the acetylene glycols. Among these, 2,4,7,9-tetramethyl-5-decine-4,7-diol is preferable.
Commercially available acetylene glycol-based surfactants include the "Surfinol" series (2,4,7,9-tetramethyl-5-decine-4,7-diol or 2,4) manufactured by Nissin Chemical Industry Co., Ltd. , 7,9-Tetramethyl-5-decine-4,7-diol ethylene oxide adduct), "Acetylenol" series manufactured by Kawaken Fine Chemicals Co., Ltd., etc.

The polyether-modified silicone-based surfactant has a structure in which the side chain and / or the hydrocarbon group at the terminal of the silicone oil is replaced with a polyether group. As the polyether group, a polyethyleneoxy group, a polypropyleneoxy group, an ethyleneoxy group (EO) and a propyleneoxy group (trimethylethyleneoxy group or propane-1,2-diyloxy group; PO) were added in a block shape or at random. A polyalkyleneoxy group is preferable, and a compound in which a polyether group is grafted on a silicone main chain, a compound in which a silicone and a polyether group are bonded in a block shape, and the like can be used.
Specific examples of the polyether-modified silicone-based surfactant include the KF series manufactured by Shin-Etsu Chemical Co., Ltd., the Silface SAG manufactured by Shin-Etsu Chemical Co., Ltd., and the BYK series manufactured by Big Chemie Japan Co., Ltd.

The pH of the water-based ink is preferably 5.5 or more, more preferably 6.0 or more, even more preferably 6.5 or more from the viewpoint of storage stability, and preferably 11 from the viewpoint of skin irritation. It is 0.0 or less, more preferably 10.0 or less, still more preferably 9.5 or less.

[Printing method]
Examples of the printing base material to which the water-based ink is applied include plain paper having high water absorption, coated paper having low water absorption, and a resin film. Examples of the coated paper include general-purpose glossy paper and multicolor foam gloss paper, and examples of the resin film include polyester film, polyvinyl chloride film, polypropylene film, polyethylene film and the like.
The water-based ink is preferably used in a printing method for printing on a resin film as a printing base material because it has excellent adhesion to a base material.
The resin film of the base material may be a biaxially stretched film, a uniaxially stretched film, or a non-stretched film, more preferably a polyester film or a stretched polypropylene film, and a corona discharge-treated polyethylene terephthalate (PET) film or corona discharge treatment. Biaxially stretched polypropylene (OPP) film is more preferable.

In particular, when the shell resin contains a structural unit derived from the ionic monomer (a-2) and a resin film subjected to corona discharge treatment is used as the printing base material, the surface of the base material imparted by the corona discharge treatment is used. The interaction between the polar group and the ionic group introduced into the shell resin of the core-shell type resin particles further improves the adhesion to the base material. From this point of view, the printing substrate is preferably a corona discharge-treated resin film, and is selected from a corona discharge-treated polyethylene terephthalate (PET) film and a corona discharge-treated biaxially stretched polypropylene (OPP) film. The above is more preferable.
The thickness of the printed substrate is preferably 5 μm or more, more preferably 10 μm or more, still more preferably 15 μm or more, and preferably 100 μm or less, more preferably 80 μm or less, from the viewpoint of substrate adhesion and availability. It is more preferably 60 μm or less, and even more preferably 40 μm or less.

With respect to the embodiments described above, the present invention further discloses the following embodiments.
<1> A resin particle dispersion containing core-shell type resin particles (A) and water.
The shell resin of the core-shell type resin particles (A) contains a structural unit derived from (meth) acrylic acid ester (a-1) having a hydrocarbon group having 4 or more and 8 or less carbon atoms.
The core resin of the core-shell type resin particles (A) has a (meth) acrylamide-based monomer (b-1) ^{having a solubility parameter of 17.0 (J / cm 3} ) ^0.5 or more and 21.0 (J / cm ³ ) ^{0.5 or less.} ) Derived from 5% by mass or more
The glass transition temperature of the core resin is 50 ° C or less,
A resin particle dispersion in which the acid value of the core-shell type resin particles (A) is 50 mgKOH / g or more and 100 mgKOH / g or less.

<2> The (meth) acrylic acid ester (a-1) is preferably one or more selected from alkyl (meth) acrylates and aromatic group-containing (meth) acrylates, and more preferably alkyl (meth). The resin particle dispersion according to <1>, which is an acrylate.
<3> The resin particle dispersion according to <2> above, wherein the alkyl (meth) acrylate preferably has an alkyl group having 4 or more and 8 or less carbon atoms, and more preferably 4 or more and 6 or less carbon atoms.

<4> The resin particle dispersion according to any one of <1> to <3> above, wherein the shell resin further contains a structural unit derived from the ionic monomer (a-2).
<5> The ionic monomer (a-2) is preferably a carboxylic acid monomer having a carboxy group, and more preferably acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and the like. The resin particle dispersion according to <4> above, which is one or more selected from 2-methacryloyloxymethyl succinic acid and more preferably one or more selected from acrylic acid and methacrylic acid.

<6> The content of the (meth) acrylic acid ester (a-1) in the shell resin monomer or the content of the structural unit derived from the (meth) acrylic acid ester (a-1) in the shell resin is. It is preferably 40% by mass or more, more preferably 50% by mass or more, further preferably 60% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, still more preferably 85% by mass or less. The resin particle dispersion according to any one of <1> to <5>.
<7> The content of the ionic monomer (a-2) in the shell resin monomer or the content of the structural unit derived from the ionic monomer (a-2) in the shell resin is preferably 5% by mass. The above <4. The above is more preferably 10% by mass or more, further preferably 15% by mass or more, and preferably 60% by mass or less, more preferably 50% by mass or less, still more preferably 40% by mass or less. > The resin particle dispersion according to any one of <6>.

<8> The acid value of the shell resin is preferably 100 mgKOH / g or more, more preferably 120 mgKOH / g or more, still more preferably 150 mgKOH / g or more, still more preferably 170 mgKOH / g or more, and preferably 280 mgKOH or more. The resin particle dispersion according to any one of <1> to <7> above, which is / g or less, more preferably 260 mgKOH / g or less, still more preferably 250 mgKOH / g or less, still more preferably 200 mgKOH / g or less.

<9> The SP value of the (meth) acrylamide-based monomer (b-1) is preferably 17.3 (J / cm ³ ) ^0.5 or more, more preferably 17.5 (J / cm ³ ) ^0.5 or more. The resin particle dispersion according to any one of <1> to <8>, preferably 20.7 (J / cm ³ ) ^0.5 or less, more preferably 20.5 (J / cm ³ ) ^{0.5 or less.} body.
<10> The (meth) acrylamide-based monomer (b-1) is preferably N-alkyl (meth) acrylamide having a linear, branched or cyclic alkyl group, aromatic group-containing (meth) acrylamide, and N-. One or more selected from alkoxymethyl (meth) acrylamide, more preferably N-tert-butyl acrylamide, N-tert-octyl acrylamide, N- (2-ethylhexyl) acrylamide, Nn-octyl acrylamide, N. -Dodecylacrylamide, Nn-heptylacrylamide, N-hexylacrylamide, N-cyclohexylmethacrylamide, N, N-dibenzylacrylamide, and N-isobutoxymethylacrylamide, which are one or more selected from the above <1>. The resin particle dispersion according to any one of <9>.

<11> The (meth) acrylamide-based monomer (b-1) is preferably N-alkyl (meth) acrylamide having a linear, branched or cyclic alkyl group, and more preferably N-alkyl having a branched alkyl group. Acrylamide is more preferably N-alkylacrylamide having a branched alkyl group having 4 or more and 8 or less carbon atoms, and even more preferably one or more selected from N-tert-butyl acrylamide and N-tert-octyl acrylamide. The resin particle dispersion according to any one of <1> to <10>.

<12> The resin according to any one of <1> to <11> above, wherein the core resin further contains a (meth) acrylic acid ester (b-2) having a hydrocarbon group having 2 or more and 18 or less carbon atoms. Particle dispersion.
<13> The hydrocarbon group of the (meth) acrylic acid ester (b-2) preferably has 3 or more carbon atoms, more preferably 4 or more carbon atoms, and preferably 12 or less, more preferably 8 or less carbon atoms. The resin particle dispersion according to <12> above.
<14> The hydrocarbon group of the (meth) acrylic acid ester (b-2) having 2 or more and 18 or less carbon atoms is preferably one or more selected from an alkyl group having 3 or more and 12 or less carbon atoms and a benzyl group. Yes, more preferably one or more selected from a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a hexyl group, an octyl group, a 2-ethylhexyl group, an octadecyl group, a cyclohexyl group, and a benzyl group. Is one or more selected from a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a hexyl group, an octyl group, a 2-ethylhexyl group, and a benzyl group, and more preferably an isobutyl group. The resin particle dispersion according to <12> or <13>.

<15> The (meth) acrylic acid ester (b-2) having a hydrocarbon group having 2 or more and 18 or less carbon atoms is preferably butyl (meth) acrylate, isobutyl (meth) acrylate, secondary butyl (meth) acrylate, and Tasha. One or more selected from lybutyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and benzyl (meth) acrylate, more preferably isobutyl (meth) acrylate. , Secondary butyl (meth) acrylate, tertiary butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and benzyl (meth) acrylate. The resin particle dispersion according to any one of <12> to <14>.

<16> The content of the (meth) acrylamide-based monomer (b-1) in the core resin monomer or the content of the structural unit derived from the (meth) acrylamide-based monomer (b-1) in the core resin is preferable. Is 7% by mass or more, more preferably 10% by mass or more, and preferably 60% by mass or less, more preferably 50% by mass or less, still more preferably 40% by mass or less, still more preferably 30% by mass or less. The resin particle dispersion according to any one of <1> to <15>, which is more preferably 20% by mass or less.
<17> The content of the (meth) acrylic acid ester (b-2) having a hydrocarbon group of 2 to 18 carbon atoms in the core resin monomer or the hydrocarbon having 2 to 18 carbon atoms in the core resin. The content of the structural unit derived from the (meth) acrylic acid ester (b-2) having a group is preferably 30% by mass or more, more preferably 40% by mass or more, still more preferably 50% by mass or more, still more. The above-mentioned <12> to <16>, preferably 70% by mass or more, preferably 95% by mass or less, more preferably 93% by mass or less, still more preferably 90% by mass or less. Resin particle dispersion.

<18> The glass transition temperature of the core resin is preferably 40 ° C. or lower, more preferably 35 ° C. or lower, still more preferably 30 ° C. or lower, still more preferably 25 ° C. or lower, still more preferably 10 ° C. or lower. Then, it is preferably −13 ° C. or higher, more preferably −10 ° C. or higher, and even more preferably −7 ° C. or higher. The resin particle dispersion according to any one of <1> to <17>.
<19> The acid value of the core resin is preferably 50 mgKOH / g or less, more preferably 30 mgKOH / g or less, still more preferably 10 mgKOH / g or less, still more preferably 0 mgKOH / g. 18> The resin particle dispersion according to any one of.

<20> The mass ratio of the content of the core resin to the shell resin in the core-shell type resin particles (A) [core resin / shell resin] is preferably 0.6 or more, more preferably 0.8 or more. , More preferably 1 or more, and preferably 3.0 or less, more preferably 2.7 or less, still more preferably 2.5 or less, still more preferably 2.3 or less. The resin particle dispersion according to any one of <19>.

<21> The acid value of the core-shell type resin particles (A) is preferably 55 mgKOH / g or more, more preferably 60 mgKOH / g or more, and 100 mgKOH / g or less, preferably 95 mgKOH / g or less, more preferably. The resin particle dispersion according to any one of <1> to <20> above, wherein is 90 mgKOH / g or less.
<22> The average particle size of the core-shell type resin particles (A) in the resin particle dispersion is preferably 10 nm or more, more preferably 20 nm or more, further preferably 40 nm or more, and preferably 150 nm or less, more preferably. The resin particle dispersion according to any one of <1> to <21>, wherein is 120 nm or less, more preferably 100 nm or less.

<23> The resin particle dispersion according to any one of <1> to <22>, which further contains a pigment.
<24> The resin particle dispersion according to <23>, wherein the pigment is a white pigment.
<25> The resin particle dispersion according to <23> or <24>, wherein titanium oxide is used as the pigment.
<26> The resin particle dispersion according to any one of <23> to <25> above, wherein titanium oxide is dispersed with a polymer dispersant.

<27> The content of the core-shell type resin particles (A) in the resin particle dispersion is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and preferably. The resin particle dispersion according to any one of <1> to <26> above, which is 50% by mass or less, more preferably 40% by mass or less, still more preferably 35% by mass or less.
<28> The content of water in the resin particle dispersion is preferably 30% by mass or more, more preferably 40% by mass or more, still more preferably 45% by mass or more, still more preferably 50% by mass or more, still more preferably. Is 53% by mass or more, and preferably 80% by mass or less, more preferably 75% by mass or less, still more preferably 70% by mass or less, still more preferably 65% by mass or less. 27> The resin particle dispersion according to any one of.
<29> When the resin particle dispersion further contains a pigment, the content of the pigment in the resin particle dispersion is preferably 3% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more. And more preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, still more preferably 20% by mass or less, any of the above <1> to <28>. The resin particle dispersion according to.
<30> When the resin particle dispersion further contains a pigment, the mass ratio of the pigment content to the core-shell type resin particles (A) in the resin particle dispersion [pigment / core-shell type resin particles (A)] is determined. Preferably 0.3 or more, more preferably 0.5 or more, still more preferably 0.8 or more, even more preferably 1.0 or more, even more preferably 1.3 or more, still more preferably 1.5 or more. The resin particles according to any one of <1> to <29> above, more preferably 1.8 or more, and preferably 4 or less, more preferably 3 or less, still more preferably 2.5 or less. Dispersion.

<31> When the resin particle dispersion further contains a water-soluble organic solvent, the content of the water-soluble organic solvent in the resin particle dispersion is preferably 0.2% by mass or more, more preferably 0.5% by mass. The above <1> to <30>, more preferably 0.8% by mass or more, and preferably 30% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less. The resin particle dispersion according to any one.
<32> When the resin particle dispersion further contains a water-soluble organic solvent, the mass ratio of the content of water to the water-soluble organic solvent in the resin particle dispersion [water / water-soluble organic solvent] is preferably 0. 5.5 or more, more preferably 1 or more, still more preferably 2 or more, even more preferably 2.5 or more, and preferably 100 or less, more preferably 50 or less, still more preferably 30 or less, even more preferably. The resin particle dispersion according to any one of <1> to <31>, which is 10 or less, more preferably 5 or less, and even more preferably 3.5 or less.
<33> The resin particle dispersion according to any one of <1> to <32>, which is a water-based ink for gravure printing.
<34> Use of the resin particle dispersion according to any one of <1> to <32> as a water-based ink for gravure printing in which the thickness of the printing substrate is 5 μm or more and 100 μm or less.

<35> A step of polymerizing the core resin monomer forming the core resin in the presence of an emulsion of the shell polymer forming the shell resin to form the core shell type resin particles (A) to obtain a resin particle dispersion. The method for producing a resin particle dispersion according to any one of <1> to <33>, which comprises I.
<36> The resin particle dispersion according to <35>, wherein the titanium oxide dispersion is further added and mixed with the resin particle dispersion obtained in step I to obtain a resin particle dispersion containing titanium oxide. Production method.
<37> The method for producing a resin particle dispersion according to <36>, wherein titanium oxide is dispersed in the titanium oxide dispersion with a polymer dispersant.
<38> The weight average molecular weight of the shell polymer is preferably 6,000 or more, more preferably 8,000 or more, still more preferably 10,000 or more, and preferably 300,000 or less, more preferably 200, The method for producing a resin particle dispersion according to any one of <35> to <37>, wherein the amount is 000 or less, more preferably 100,000 or less, still more preferably 50,000 or less.

<39> A printing method in which the resin particle dispersion according to any one of <1> to <33> is used as a water-based ink and printed on a resin film as a printing base material.
<40> The printing substrate is preferably one or more selected from a corona discharge-treated resin film, more preferably a corona discharge-treated polyethylene terephthalate film, and a corona discharge-treated biaxially stretched polypropylene film. The printing method according to <39> above.
<41> The thickness of the printing substrate is preferably 5 μm or more, more preferably 10 μm or more, further preferably 15 μm or more, and preferably 100 μm or less, more preferably 80 μm or less, still more preferably 60 μm or less, further. The printing method according to <39> or <40>, which is preferably 40 μm or less.

In the following production examples, examples and comparative examples, "parts" and "%" are "parts by mass" and "% by mass" unless otherwise specified. The various physical properties were measured by the following methods.

(1) Measurement of weight average molecular weight of polymer Gel chromatography method using a solution prepared by dissolving phosphoric acid and lithium bromide in N, N-dimethylformamide at concentrations of 60 mmol / L and 50 mmol / L, respectively, as an eluent. [GPC device (model: HLC-8320GPC, manufactured by Tosoh Corporation), column (TSKgel SuperAWM-H, TSKgel SuperAW3000, TSKgel guard polymer AW-H, above, trade name manufactured by Tosoh Corporation), flow velocity: 0.5 mL / By [min], a monodisperse polystyrene kit [PStQuick B (F-550, F-80, F-10, F-1, A-1000), PStQuick C (F-288, F-40,) whose molecular weight is known as a standard substance. F-4, A-5000, A-500), above, trade name manufactured by Tosoh Corporation] was used for the measurement.
For the measurement sample, 0.1 g of polymer was mixed with 10 mL of the eluent in a glass vial, stirred at 25 ° C. for 10 hours with a magnetic stirrer, and a syringe filter (trade name: DISMIC-13HP, membrane filter material: hydrophilic) was used. The one filtered with PTFE, pore size 0.2 μm, manufactured by Advantech Co., Ltd.) was used.

(2-1) Measurement of average primary particle size of titanium oxide The average primary particle size of titanium oxide is 500 titanium oxides by image analysis using a transmission electron microscope "JEM-2100" (manufactured by Nippon Denshi Co., Ltd.). The primary particles were extracted, the particle size was measured, and the average was calculated and calculated as the number average particle size. When titanium oxide had a major axis and a minor axis, the major axis was used for calculation.
(2-2) Measurement of Average Particle Size of Titanium Oxide Dispersion Using a laser diffraction / scattering type particle size distribution measuring device "LA950" (manufactured by HORIBA, Ltd.), the refractive index of titanium oxide is set to 2.75 and refraction is performed. Using water having a refractive index of 1.333 as a dispersion medium, the scale of the circulation speed was set to "5" and the scale of the intensity of the ultrasonic wave was set to "3", and the measurement was performed after irradiation for 1 minute. The value of the volume median particle diameter (D ₅₀ ) at this time was taken as the average particle diameter of the particles of the dispersion.

(3) Measurement of average particle size of resin particle dispersion and shell polymer emulsion A cumulant analysis is performed using the laser particle analysis system "ELSZ-1000" (manufactured by Otsuka Electronics Co., Ltd.), and the average particle size of the cumland obtained by the measurement is determined. The average particle size of the resin particle dispersion or the shell polymer emulsion was used. The measurement conditions were a temperature of 25 ° C., an angle between the incident light and the detector of 165 °, and the number of integrations was 100 times, and the refractive index of water (1.333) was input as the refractive index of the dispersion solvent. The concentration of the measurement sample was 5 × 10 ^-3 % (converted to solid content concentration).

(4-1) Measurement of solid content concentration of resin particle dispersion and shell polymer emulsion Using an infrared moisture meter (manufactured by Ketsuto Kagaku Kenkyusho Co., Ltd., trade name: FD-230), 5 g of the aqueous dispersion was dried at a drying temperature of 150. Dry under the conditions of ° C. and measurement mode 96 (monitoring time 2.5 minutes / fluctuation width 0.05%) to remove the wet base moisture (mass%) of the aqueous dispersion (resin particle dispersion or shell polymer emulsion). It was measured. The solid content concentration was calculated according to the following formula.
Solid content concentration (% by mass) = 100-Wet base water content of aqueous dispersion (% by mass)
(4-2) Measurement of solid content concentration of polymer solution and pigment dispersion Weigh 10.0 g of sodium sulfate homogenized in a desiccator into a 30 mL polypropylene container (φ = 40 mm, height = 30 mm) and place it there. After 1.0 g of the sample was added and mixed, the mixture was accurately weighed, maintained at 105 ° C. for 2 hours to remove volatile matter, and further left in a desiccator for 15 minutes, and then the mass was measured. The mass of the sample after removing the volatile matter was taken as the solid content and divided by the mass of the added sample to obtain the solid content concentration.

Production Example 1-1 (Production of Polymer Dispersant for Dispersing Titanium Oxide)
182 g of water was charged into 2 L of a glass reaction vessel equipped with a dropping funnel, and the temperature was raised to 80 ° C. in a nitrogen atmosphere.
Next, under a nitrogen gas atmosphere, methoxypolyethylene glycol monomethacrylate (ethylene oxide (EO) average addition mole number n = 23, manufactured by Shin-Nakamura Chemical Industry Co., Ltd., trade name "NK ester M-230G") 314. A monomer solution of 1 g and 69.5 g of methacrylic acid, 21.1 g of a 2-mercaptoethanol (polymerization chain transfer agent) aqueous solution having a concentration of 15% as a dropping solution 2, and ammonium persulfate (polymerization initiator) having a concentration of 6% as a dropping solution 3. ) 84.1 g of the aqueous solution was gradually added dropwise into the reaction vessel over 90 minutes at the same time. After completion of the dropping, the mixture was aged at 80 ° C. for 1 hour.
Then, the mixture was cooled to 40 ° C., 26.9 g of a 48% aqueous sodium hydroxide solution was added, and 484.3 g of water was added so that the solid content concentration became 40%, and a polymer dispersant (weight average molecular weight of polymer: 24) was added. A solution of (000) was obtained.

Production Example 2-1 (Production of Titanium Oxide Dispersion)
6 g of the polymer dispersant solution obtained in Production Example 1-1 and 2 g of ion-exchanged water were mixed and dissolved, and the solution was put into a 1000 mL polyethylene bottle and titanium oxide (rutyl type: manufactured by Ishihara Sangyo Co., Ltd., CR- 80, Al / Si treatment, average primary particle size 250 nm) 120 g, ion-exchanged water 88 g, 2 mm zirconia beads 1476 g are added, and dispersion treatment is performed at 250 rpm for 10 hours on a tabletop pot mill stand (Aswan Co., Ltd.). It was.
After the dispersion treatment, the zirconia beads were removed using a mesh, and the solid content concentration was adjusted with water to obtain a titanium oxide dispersion (solid content concentration 51%) having an average particle size of 325 nm.

(Manufacturing of shell polymer emulsion)
Production Example 3-1
(1) Preparation of Shell Polymer P1 Solution A monomer mixed solution was prepared by mixing 75.8 parts of tertiary butyl methacrylate and 24.2 parts of acrylic acid. In the reaction vessel, 5 parts of methyl ethyl ketone (hereinafter referred to as "MEK"), 2.5 parts of 2-mercaptoethanol (polymerization chain transfer agent), and 10% of the above-mentioned monomer mixture are mixed and replaced with nitrogen gas. Was done enough.
On the other hand, in the dropping funnel, the remaining 90% of the monomer mixed solution, 2.25 parts of the polymerization chain transfer agent, 75 parts of MEK, and an azo radical polymerization initiator (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 2, 2'- A mixture of 2.0 parts of azobis (2,4-dimethylvaleronitrile) was added, and the temperature was raised to 77 ° C. while stirring the monomer mixture in the reaction vessel under a nitrogen atmosphere, and the mixture in the dropping funnel was added. Was added dropwise over 5 hours. After completion of the dropping, a solution prepared by dissolving 0.5 part of the polymerization initiator in 5 parts of MEK was added, further reacted at 77 ° C. for 2 hours, and finally MEK was added so that the solid content concentration became 55%, and the shell polymer was added. A P1 solution was obtained. The glass transition temperature (Tg) of the polymer P1 was 106 ° C., the acid value was 180 mgKOH / g, and the weight average molecular weight was 16,000.
(2) Production of Emulsion EM1 of Shell Polymer P1 100 g of polymer P1 solution was placed in a 1000 mL separable flask, and while stirring (200 rpm) with a stirring blade, 5N hydroxide was added so that the degree of neutralization was 60%. After dropping the aqueous sodium solution, 372 g of ion-exchanged water was added dropwise at 10 mL / min. Then, the solvent was removed and dehydrated by an evaporator to obtain a shell polymer emulsion EM1 (acid value: 180 mgKOH / g, neutralization degree 60%) having an average particle size of 15 nm and a resin solid content of 20%.

Production Example 3-2 to Production Example 3-3
Emulsion of shell polymer P2 having a resin solid content of 20% and emulsion of shell polymer P3 in the same manner as in Production Example 3-1 except that the composition of the resin monomer in the shell portion was changed to Table 1 in Production Example 3-1. EM3 was obtained. Table 1 shows the glass transition temperature (Tg), acid value, weight average molecular weight, neutralization degree, and average particle size of the shell polymer emulsions of the shell polymers P2 and P3.

Each notation in Table 1 is as follows.
tBMA: tertiary butyl methacrylate CHMA: cyclohexyl methacrylate AA: acrylic acid

Example 1
(1) Production of Resin Particle Dispersion Containing Core-Shell Type Resin Particles (A1) 200 g of the emulsion EM1 obtained in Production Example 3-1 and 12.2 g of ion-exchanged water were put into a 1000 mL separable flask and stirred. While (100 rpm), 3.7 g of N-tert-butylacrylamide (manufactured by MCC Unitech Co., Ltd., SP value: 20.2 (J / cm ³ ) ^0.5 ) and 33.5 g of isobutyl acrylate were added as the core resin monomer in advance. Was added, and the temperature was raised to 75 ° C. with stirring.
A 9.3 g aqueous solution of potassium persulfate (polymerization initiator) having a concentration of 4% was gradually added dropwise thereto over 90 minutes. After completion of the dropping, the mixture was aged at 80 ° C. for 1 hour. Then, the mixture was cooled to room temperature to obtain a resin particle dispersion containing core-shell type resin particles (A1) having a solid content concentration of 30%. Table 2 shows the glass transition temperature (Tg) of the core resin, the acid value of the resin particles (A1), and the mass ratio [core resin / shell resin].
(2) Production of Aqueous Ink 1 23.3 g of the resin particle dispersion containing the obtained core-shell type resin particles (A1), 30 g of the titanium oxide dispersion produced in Production Example 2-1 and 5 g of diethylene glycol monoisobutyl ether. , 1,2-Propanediol 15g, acetylene glycol-based surfactant "Surfinol 440" (2,4,7,9-tetramethyl-5-decine-4,7-diol ethylene oxide (3.5 mol) added 1 g of product, manufactured by Nissin Chemical Industry Co., Ltd., 1 g of polyether-modified silicone-based surfactant "KF6011" (PEG-11 methyl ether dimethicone, manufactured by Shin-Etsu Chemical Industry Co., Ltd.), and 24.7 g of ion-exchanged water are mixed. Aqueous ink 1 was obtained.

Example 2
(1) Production of Resin Particle Dispersion Containing Core-Shell Type Resin Particles (A2) In Example 1, the same procedure as in Example 1 was carried out except that the emulsion EM1 was changed to the emulsion EM3, and the core-shell type having a solid content concentration of 30%. A resin particle dispersion containing the resin particles (A2) was obtained.
(2) Production of Water-based Ink 2 A water-based ink 2 was obtained in the same manner as in Example 1 except that the resin particle dispersion containing the obtained core-shell type resin particles (A2) was used.

Example 3
(1) Production of Resin Particle Dispersion Containing Core-Shell Type Resin Particles (A3) In Example 1, N-tert-butylacrylamide was used as the core resin monomer in N-tert-octylacrylamide (manufactured by MCC Unitech, SP value). : 17.9 (J / cm ³ ) ^0.5 ) was carried out in the same manner as in Example 1 to obtain a resin particle dispersion containing core-shell type resin particles (A3) having a solid content concentration of 30%.
(2) Production of Water-based Ink 3 A water-based ink 3 was obtained in the same manner as in Example 1 except that the resin particle dispersion containing the obtained core-shell type resin particles (A3) was used.

Example 4
(1) Production of Resin Particle Dispersion Containing Core-Shell Type Resin Particles (A4) 200 g of the emulsion EM1 obtained in Production Example 3-1 and 91.0 g of ion-exchanged water were put into a 1000 mL separable flask and stirred. While (100 rpm), a mixture of 7.4 g of N-tert-octylacrylamide and 67.0 g of isobutyl acrylate was added as a core resin monomer in advance, and the temperature was raised to 75 ° C. with stirring.
18.6 g of an aqueous solution of potassium persulfate having a concentration of 4% was gradually added dropwise thereto over 90 minutes. After completion of the dropping, the mixture was aged at 80 ° C. for 1 hour. Then, the mixture was cooled to room temperature to obtain a resin particle dispersion containing core-shell type resin particles (A4) having a solid content concentration of 30%.
(2) Production of Water-based Ink 4 A water-based ink 4 was obtained in the same manner as in Example 1 except that the resin particle dispersion containing the obtained core-shell type resin particles (A4) was used.

Example 5
(1) Production of Resin Particle Dispersion Containing Core-Shell Type Resin Particles (A5) 200 g of the emulsion EM2 obtained in Production Example 3-2 and 86.8 g of ion-exchanged water were put into a 1000 mL separable flask and stirred. While (100 rpm), a mixture of 7.3 g of N-tert-octyl acrylamide and 65.3 g of isobutyl acrylate was added in advance, and the temperature was raised to 75 ° C. with stirring.
18.1 g of an aqueous solution of potassium persulfate having a concentration of 4% was gradually added dropwise thereto over 90 minutes. After completion of the dropping, the mixture was aged at 80 ° C. for 1 hour. Then, the mixture was cooled to room temperature to obtain a resin particle dispersion containing core-shell type resin particles (A5) having a solid content concentration of 30%.
(2) Production of Water-based Ink 5 A water-based ink 5 was obtained in the same manner as in Example 1 except that the resin particle dispersion containing the obtained core-shell type resin particles (A5) was used.

Example 6
(1) Production of Resin Particle Dispersion Containing Core-Shell Type Resin Particles (A6) 200 g of the emulsion EM1 obtained in Production Example 3-1 and 12.2 g of ion-exchanged water were put into a 1000 mL separable flask and stirred. While (100 rpm), a mixture of 1.9 g of tert-butyl acrylamide and 35.4 g of isobutyl acrylate was added in advance, and the temperature was raised to 75 ° C. with stirring.
A 9.3 g aqueous solution of potassium persulfate having a concentration of 4% was gradually added dropwise thereto over 90 minutes. After completion of the dropping, the mixture was aged at 80 ° C. for 1 hour. Then, the mixture was cooled to room temperature to obtain a resin particle dispersion containing core-shell type resin particles (A6) having a solid content concentration of 30%.
(2) Production of Water-based Ink 6 A water-based ink 6 was obtained in the same manner as in Example 1 except that the resin particle dispersion containing the obtained core-shell type resin particles (A6) was used.

Comparative Example 1
(2) Production of Water-based Ink C1 In the production of the water-based ink of Example 1, the emulsion EM1 obtained in Production Example 3-1 was used instead of 23.3 g of the resin particle dispersion containing the core-shell type resin particles (A1). Using 35.0 g, the mixture was blended in the same manner as in the production of the water-based ink 1 of Example 1 except that the amount of ion-exchanged water was changed to 13.0 g, to obtain a water-based ink C1.

Comparative Example 2
(1) Production of Resin Particle Dispersion Containing Core-Shell Type Resin Particles (AC2) In Example 1, the amount of isobutyl acrylate was 37.5 g as the core resin monomer, except that N-tert-butylacrylamide was not used. The same procedure as in Example 1 was carried out to obtain a resin particle dispersion containing core-shell type resin particles (AC2) having a solid content concentration of 30%.
(2) Production of Water-based Ink C2 A water-based ink C2 was obtained in the same manner as in Example 1 except that the resin particle dispersion containing the obtained core-shell type resin particles (AC2) was used.

Comparative Example 3
(1) Production of Resin Particle Dispersion Containing Core-Shell Type Resin Particles (AC3) In Example 1, N-tert-butyl acrylamide was used as a core resin monomer in diacetone acrylamide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., SP). The same procedure as in Example 1 was carried out except that the value was changed to 22.0 (J / cm ³ ) ^0.5 ), but core-shell type resin particles could not be obtained because the system gelled.

Comparative Example 4
(1) Production of Resin Particle Dispersion Containing Core-Shell Type Resin Particles (AC4) 200 g of the emulsion EM1 obtained in Production Example 3-1 and 12.2 g of ion-exchanged water were put into a 1000 mL separable flask and stirred. While (100 rpm), 1.2 g of N-tert-butyl acrylamide and 36.0 g of isobutyl acrylate were previously mixed as a core resin monomer, and the mixture was stirred and heated to 75 ° C. as in the example.
A 9.3 g aqueous solution of potassium persulfate having a concentration of 4% was gradually added dropwise thereto over 90 minutes. After completion of the dropping, the mixture was aged at 80 ° C. for 1 hour. Then, the mixture was cooled to room temperature to obtain a resin particle dispersion containing core-shell type resin particles (AC4) having a solid content concentration of 30%.
(2) Production of Water-based Ink A water-based ink C4 was obtained in the same manner as in Example 1 except that the resin particle dispersion containing the obtained core-shell type resin particles (AC4) was used.

[Evaluation]
(Evaluation of substrate adhesion)
(1) Preparation of printed matter Using a gravure proofing machine (manufactured by RK Print Coat Instruments Ltd, "K Printing Proofer"), a honeycomb screen with 250 lines and a depth of 10 μm was used as a gravure plate, and obtained in Examples and Comparative Examples. Using the water-based ink obtained, the following corona discharge-treated OPP film was printed as a printing substrate at a speed of 15 m / min, and then dried at 60 ° C. for 1 hour to obtain a gravure printed matter.
(Corona discharge processing OPP film)
OPP # 50: FOS-AQ, # 50 (thickness 50 μm), manufactured by Futamura Chemical Co., Ltd. OPP # 20: FOR-AQ, # 20 (thickness 20 μm), manufactured by Futamura Chemical Co., Ltd. (2) Tape peeling test 25 ° C environment Below, an adhesive surface of cellophane tape (manufactured by Nichiban Co., Ltd., 18 mm width) was attached to the 100% density portion of the gravure printed matter, and the tape was strongly adhered with the pad of the hand, and then the tape was peeled off as soon as possible. From the ratio of the peeled area, the substrate adhesion was evaluated according to the following criteria. The results are shown in Table 2.
(Evaluation criteria)
A: There is no peeling of the print.
B: There is some peeling of the print (the ratio of the peeled area is less than 10%).
C; There is peeling of the print (the ratio of the peeled area is 10% or more and less than 30%).
D; There is peeling of the print (the ratio of the peeled area is 30% or more and less than 40%).
E; There is considerable peeling of the print (the ratio of the peeled area is 40% or more).
If the evaluation is C or higher (that is, the ratio of the peeled area is less than 30%), it is practical in the application where the printed matter is not rubbed, and if the evaluation is B or higher (that is, the ratio of the peeled area is less than 10%). It is also practical in applications where printed matter is rubbed.

The notations in Table 2 are as follows.
tBuAAm: N-tert-butyl acrylamide tOAAm: N-tert-octyl acrylamide iBA: Isobutyl acrylate DAAm: Diacetone acrylamide

From Table 2, it can be seen that the water-based inks of Examples 1 to 6 are superior in substrate adhesion to the water-based inks of Comparative Examples 1, 2 and 4.
Since Comparative Example 1 is a water-based ink using a resin particle emulsion having no core-shell structure, the adhesion to the base material is inferior regardless of the thickness of the resin film.
In Comparative Example 2, since the core resin does not contain a structural unit derived from a (meth) acrylamide-based monomer, the substrate adhesion to a thin resin film is inferior.
In Comparative Example 3, since the SP value of the (meth) acrylamide-based monomer contained in the core resin is more than 21.0 (J / cm ³ ) ^0.5 , the system gels during production, and the core-shell type resin particles. Could not be obtained.
In Comparative Example 4, since the content of the constituent unit derived from the (meth) acrylamide-based monomer in the core resin is less than 5% by mass, the substrate adhesion to the thin resin film is inferior.

Claims (15)

A resin particle dispersion containing core-shell type resin particles (A) and water.
The shell resin of the core-shell type resin particles (A) contains a structural unit derived from (meth) acrylic acid ester (a-1) having a hydrocarbon group having 4 or more and 8 or less carbon atoms.
The core resin of the core-shell type resin particles (A) has a (meth) acrylamide-based monomer (b-1) ^{having a solubility parameter of 17.0 (J / cm 3} ) ^0.5 or more and 21.0 (J / cm ³ ) ^{0.5 or less.} ) Derived from 5% by mass or more
The glass transition temperature of the core resin is 50 ° C or less,
A resin particle dispersion in which the acid value of the core-shell type resin particles (A) is 50 mgKOH / g or more and 100 mgKOH / g or less. The resin particle dispersion according to claim 1, wherein the core resin further contains a structural unit derived from a (meth) acrylic acid ester (b-2) having a hydrocarbon group having 2 or more and 18 or less carbon atoms. 2. The hydrocarbon group of the (meth) acrylic acid ester (b-2) having 2 or more and 18 or less carbon atoms is one or more selected from an alkyl group having 3 or more and 12 or less carbon atoms and a benzyl group. The resin particle dispersion described. The resin particle dispersion according to any one of claims 1 to 3, wherein the shell resin further contains a structural unit derived from an ionic monomer (a-2). The resin particle dispersion according to claim 4, wherein the content of the structural unit derived from the (meth) acrylic acid ester (a-1) in the shell resin is 40% by mass or more and 95% by mass or less. The resin particle dispersion according to any one of claims 1 to 5, wherein the acid value of the shell resin is 100 mgKOH / g or more and 280 mgKOH / g or less. Any of claims 1 to 6, wherein the mass ratio [core resin / shell resin] of the content of the core resin to the shell resin in the core-shell type resin particles (A) is 1 or more and 2.5 or less. The resin particle dispersion described in Crab. The resin particle dispersion according to any one of claims 1 to 7, wherein the water content is 30% by mass or more and 80% by mass or less. The resin particle dispersion according to any one of claims 1 to 8, further containing a pigment. The resin particle dispersion according to claim 9, wherein the pigment is a white pigment. The resin particle dispersion according to any one of claims 1 to 10, which is a water-based ink for gravure printing. Use of the resin particle dispersion according to any one of claims 1 to 10 as a water-based ink for gravure printing in which the thickness of the printing substrate is 5 μm or more and 100 μm or less. In the presence of an emulsion of the shell polymer forming the shell resin, the step I of polymerizing the core resin monomer forming the core resin to form the core shell type resin particles (A) to obtain a resin particle dispersion is included. , The method for producing a resin particle dispersion according to any one of claims 1 to 11. A printing method in which the resin particle dispersion according to any one of claims 1 to 11 is used and printed on a resin film as a printing base material. The printing method according to claim 14, wherein the thickness of the printing substrate is 5 μm or more and 100 μm or less.